Whole blood analyses in porous media

Abstract

Method and apparatus for analyzing whole blood samples which feature impregnating a gel medium used for the analysis of the whole blood sample with an inert substance. When the whole blood sample is placed on the gel medium, the inert substance diffuses from the gel as the plasma solutes of the blood diffuse into the gel. The amount of the inert substance diffusing from the gel medium is inversely proportional to the hematocrit of the blood sample. In one embodiment, plasma solutes are caused to react with one or more reagents in the gel medium to assay various specific analytes. Also, the hematocrit, indicated by the diffusion rate of the inert substance from the gel, is determined and used to correct such assay.

What is claimed is: 
     
       1. A method of determining the concentration of particulate in a solution, comprising the steps of: (a) contacting a surface of a medium containing an inert substance with a solution containing particulate, said inert substance being inert with respect to said solution and said particulate;   (b) diffusing at least a portion of said solution across said surface into said medium;   (c) diffusing at least a portion of said inert substance from within said medium across the surface contacted by said solution, the diffusion of said inert substance from the medium being indicative of the amount of particulate in said solution; and   (d) determining the concentration of said particulate in said solution as a function of said inert substance diffusing from said medium.   
     
     
       2. A method of determining hematocrit in a whole blood sample, comprising the steps of: (a) contacting a surface of a porous medium containing a water soluble inert substance with a whole blood sample, said inert substance being inert with respect to said whole blood sample;   (b) diffusing for a period of time at least a portion of plasma solutes of said whole blood sample across said surface into said medium;   (c) cross-diffusing for a corresponding period of time at least a portion of said inert substance from within said medium across the surface contacted by said whole blood, and   (d) determining the concentration of said inert substance diffused from within said medium as indicative of the hematocrit of said whole blood sample.   
     
     
       3. The apparatus of claim 2, wherein said inert substance is a colored indicator substance. 
     
     
       4. The apparatus of claim 2, wherein said inert substance is polyhydroxylated. 
     
     
       5. The apparatus of claim 2, wherein said inert substance is a glycoside. 
     
     
       6. The apparatus of claim 2, wherein said inert substance is vitamin B-12 (cyanocobalamin). 
     
     
       7. The method of claim 2, comprising the further step of limiting said diffusing steps (b) and (c) to a controlled period of time. 
     
     
       8. The method of claim 2, further comprising the step of: (e) measuring the amount of inert substance remaining in said medium after diffusion thereof, as an indication of the hematocrit of said whole blood sample.   
     
     
       9. The method of claim 2, further comprising the step of: (e) washing said surface of said medium to remove any portion of said whole blood sample remaining on said surface after diffusion step (b).   
     
     
       10. The method of claim 2, wherein said medium is transparent and said inert substance has a color, the method comprising the further step of: (d) measuring said hematocrit of said whole blood sample by detecting the depth of color of said inert substance in said medium.   
     
     
       11. The method of claim 2, wherein said medium contains an enzyme for reaction with an analyte of said whole blood sample, the method comprising the further step of: (d) measuring the rate of reaction of the enzyme.   
     
     
       12. The method of claim 2, wherein the contacting step (a) includes agitating said whole blood sample upon said surface of said medium. 
     
     
       13. The method of claim 2, wherein the diffusing step (b) comprises the further steps of: (f) supporting said whole blood sample on a carrier; and   (g) contacting said carrier to said medium to effect diffusion of said plasma solutes of said whole blood sample into said medium.   
     
     
       14. The method of claim 13, wherein said carrier is a porous medium, and the supporting step (f) includes impregnating said porous medium with said whole blood sample. 
     
     
       15. The method of claim 2, wherein the contacting step (a) includes dispensing said whole blood sample to overlap a prescribed surface area of said medium. 
     
     
       16. The method of claim 15, comprising the further step of defining said prescribed surface area in planar fashion. 
     
     
       17. The apparatus of claim 2, wherein said porous medium is a gel. 
     
     
       18. The apparatus of claim 17, wherein said gel is a hydrocolloid. 
     
     
       19. The apparatus of claim 17, wherein the gel is transparent. 
     
     
       20. The apparatus of claim 17, wherein said gel is selected from a group of materials consisting of: gelatin, gelatin derivatives, hydrophilic cellulose derivatives, polysaccharides, gum arabic, agarose, water-soluble polyvinyl compounds, and acrylamide polymers. 
     
     
       21. The method of claim 2, further comprising the steps of: (e) supporting a plurality of porous media on a unitary support;   (f) contacting each of said plurality of porous media with a whole blood sample, one sample for each of said porous media; and   (g) determining the concentration of an inert substance diffusing from each of said porous media as indicative of the hematocrit of the respective whole blood sample in contact therewith.   
     
     
       22. The method of claim 21, wherein the medium comprises a reagent for reaction with an analyte in said plasma solutes, and wherein the method further comprises the step of: (e) measuring a reaction of said reagent with said analyte.   
     
     
       23. The method of claim 22, further comprising the step of: (f) correcting the measuring step (e) by a factor dependent upon the hematocrit of said whole blood sample.   
     
     
       24. The method of claim 22, wherein diffusion of said inert substance provides a first color indication and said reaction of said reagent with said analyte provides a second color indication, said first and second color indications, respectively, being indicative of the hematocrit of said whole blood sample and the amount of analyte in said whole blood sample, the method comprising the further step of: (f) determining from said first and second color indications the concentration of said analyte in said blood sample.   
     
     
       25. An apparatus for determining hematocrit of a whole blood sample, said apparatus comprising: a gel mass having an exposed prescribed surface area adapted to receive a whole blood sample, whereby contact of said prescribed surface area by said whole blood sample for a given period of time will diffuse an aliquot of plasma solutes from said whole blood sample into said gel mass;   a water soluble substance contained within said gel mass, said substance being inert with respect to any part of said whole blood sample and diffusable across said prescribed surface area when said gel mass is contacted to said whole blood sample, the quantity of said inert substance diffused from said gel mass being indicative of the hematocrit of said whole blood sample;   a support for carrying said gel mass and defining said prescribed surface area;   a reagent disposed within said gel mass for forming a detectable color-reaction product with at least one constituent of said whole blood sample, the presence of said inert substance within said gel mass in no way interfering with or affecting the detection of said color-reaction product; and   means for independently measuring the said color-reaction product and, also, the amount of said inert substance in either said whole blood sample or said gel mass after said diffusion.   
     
     
       26. The apparatus of claim 25, wherein said support comprises a rigid substrate having said gel mass disposed on one end thereof and a handle disposed on a distal end thereof, and adhesive means for binding said gel mass to said one end of said substrate, said one end of said substrate being immersible in said whole blood sample in dip stick fashion. 
     
     
       27. The apparatus of claim 25, wherein said support comprises an elongated substrate surface defining a well at one end for containing said gel mass. 
     
     
       28. The apparatus of claim 25, wherein said support is an elongated flexible web, and said gel mass comprises at least one strip supported by said web and containing a given quantity of a reagent, said analyte being reactive with said reagent. 
     
     
       29. The apparatus of claim 25, wherein said support is an elongated flexible web and said gel mass comprises at least two separate strips supported by said web, said strips containing given quantities of different reagents, respectively, different respective analytes being reactive with said different reagents. 
     
     
       30. The apparatus of claim 25, further comprising a carrier, means for moving portions of said carrier in contiguous overlapping relationship with said gel mass, said carrier supporting said whole blood sample, whereby at least a portion of plasma solutes of said whole blood sample is caused to diffuse into said gel mass from said carrier. 
     
     
       31. The apparatus of claim 25, wherein said inert substance is a glycoside. 
     
     
       32. The apparatus of claim 25, wherein said inert substance is vitamin B-12 (cyanocobalamin). 
     
     
       33. An automated system for determining the hematocrit of successive whole blood samples comprising: a continuous substrate supporting a plurality of porous media, at least selected ones of said media having exposed prescribed surface areas and containing a known concentration of a water soluble substance inert with respect to any part of said whole blood samples and, also, a given quantity of reagent for forming a color-reaction product with a particular analyte in said whole blood sample, said inert substance being diffusable from said selected media and soluble in said whole blood sample when contacted to said surface areas, a sample dispensing station for dispensing a whole blood sample onto the exposed surface area of each of said selected media for a controlled period of time, a measuring station for independently determining the color-reaction product formed within said selected media and, also, the quantity of said inert substance diffused from each of said selected media, as indicative of the hematocrit of said respective whole blood samples. 
     
     
       34. The automated system of claim 33, wherein said dispensing means includes means for delivering said whole blood sample in dropwise fashion onto said selected porous media. 
     
     
       35. The automated system of claim 33, wherein said dispensing means includes: means for delivering said whole blood samples in successive dropwise fashion onto a movable web and means for advancing said web into contact with said selected porous media supported on said continuous substrate. 
     
     
       36. The automated system of claim 33, wherein a portion of plasma solutes of whole blood sample is diffused into said porous media during said period of time, and further including means for removing undiffused portions of said sample from said porous media after said period of time. 
     
     
       37. The automated system of claim 33, wherein said quantity of reagent in each gel body is in excess of the quantity of said different analyte diffused into said gel body during said period of time. 
     
     
       38. The automated system of claim 33, wherein the dispensing station further comprises agitating means for agitating the whole blood samples.